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Obscurus Crusade  |  Costuming  |  Imperial Guard & Imperium  |  Cadian Standard Flack - An adventure in rotocasting

Author Topic: Cadian Standard Flack - An adventure in rotocasting  (Read 9419 times)

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Offline The Kaiser

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Cadian Standard Flack - An adventure in rotocasting
« on: September 09, 2014, 06:09:13 PM »
Some of you might have seen my buddy Jeff and I's Imperial guard costumes during Dragoncon, and I ended up get a lot of questions from folks looking to do the same/curious of what it's made of.

Now, full disclaimer, this was my first adventure into rotocasting. As someone who had always capitalized on foam and fabric on the past, I wanted something harder without the tooling, weight and general headache of fiberglass and pepekura. Also something easily reproducible, should I want to create more.

So down into the rabbit hole I went.

Rotocasting, what is it?
Rotocasting is the practice of duplicating a master mold by pouring a two part resin into a negative rubber silicone mold and removing it to create a hollow, perfect replica. It's used often for making props of guns and statues.

What are the benefits?
Your finished pieces are hard, durable and light. As much an an injection molded costume helmet you might buy from a store. Neither my trooper nor I broke anything significant during the whole weekend.

You can pop out replicas quickly, the prep work gone into one greave can create multiples at the end of the day.

You can cast in a wide spectrum of materials, from hard impact resistant plastic you might as well use for paintball armour, to rubbers, to semi-flexible plastics suitable for ab-ribbing and other places that will need to bend.

If you're diligent about your sanding and your molds are good, I haven't seen anything that can compare to the quality of a nicely sanded, painted and polished rotocast piece of armour.

What are the drawbacks?
Cost. Goddamn. For the two of these the material cost is right around 800, give or take 100. On the other hand, once I was done with set-up, I could cast an entirely new set of armour for $90 in material cost.

Time. The set-up time is ridiculous. For these two costumes alone I spent well over 300 hours. For only making two costumes, I felt like a royal idiot putting so much set up into something I could have done with EVA in a few hours. Sure, it may not look as good, but goddamn. However now that the set-up is done, popping out a new set of flak only takes 8 hours, not including tooling.

Son, you gonna need a lot of space and a table you don't care about. This stuff gets everywhere and is unapologetic towards wood, fabric, concrete and anything else under the sun. It'll bleed through paper, it does not wash off, you will be buying multiple packs of plastic gloves and popsicle sticks and it will still get EVERYWHERE.

Hard plastics mean hard tooling. I put in tens of hours into sanding all by itself and it could have stood to have quite a bit more.

Hard plastics mean hard fuckups. If you miss a registration bump and end up with a piece that's unapologetically bent in a way that a heat gun can't hope to fix, you just ruined $16 worth of resin in less than a half hour.

Would you recommend rotocasting?
For a one-off set? To people I hate, and psychopaths, yes. To anyone who wants to make duplicates of their armour relatively cheaply, absolutely. It's most effective with small detailed pieces, like helmets, props, armor plates and sigils and things. I would not recommend it for larger pieces like space marine pauldrons. It'll be expensive, brittle (or heavy) and not worth the set-up time.

Well it turns out I'm a psychopath, what do I need?

A lot of space in a well ventilated area
Non-latex gloves (the sulfur keeps your rubber from setting)
A respirator, or at the very least, dust masks
Popsicle sticks. Lots of them
Paper cups, lots of them.
Calipers and t-square

Whatever you intend to sculpt with, I use insulation foam (the blue or pink stuff, I like those big 2inch thick sheets from hardware depots)
Hot glue and gun
A large knife or foam cutting wire (I like those little thin box cutters that can be bent with relative ease to plane the foam. There's pictures of the one I use below)
plasticine clay
Sandpaper of varying grits (with a sanding sponge and a block of wood, for round or flat surfaces)

A two part silicone rubber I used 4 gallons of this
A silicone rubber thickener, for the outer layers and edges, Again, smooth-on provides.
Clothes you never want to see again
Plastipaste, plaster of paris, expanding foam, anything that will create a HARD, light shell.

Whatever two-part plastic you intend to recast in, I found I had best success with Smooth-Cast 65D and ended up using about 6 gallons of it in the end, with one screwed up chest plate and one greave.
Black plastic coloring pigment, which was a godsend when it came to scrapes that might otherwise show through the paint, or a break that had to be repaired. The armour looked great from start to end. Without it, the casts all end up bright white.

Finishing and Painting
A hand sander or rotary sander. Please. For the love of god.
A dremel. After this stuff cures for 24 hours an exacto is not going to get you anywhere besides an emergency ward.
A plastic primer in silver or black, and whatever paints you intend to use.
I had pretty good luck sticking on d-rings to the armour with a bit of plastic inclined epoxy. Only one came off during the con and was easily fixed with a bit of super glue.

How do?

Here comes the part that's the most frustrating to explain. I don't have any plans or patterns or unfolds, everything you see below was eyeballed and sketched freehand, and then checked, checked and checked again with a mirror and calipers. The result was far from perfect, but I digress. This is the process.

Before I start, I need a good mental image of what I'm going to work on, so I generally sketch it over and over until I understand all the angles and ratios. Then I match up some of the areas to how big they would need to be on the body, measure that and extrapolate, and start sketching out the part until I'm generally satisfied. Try to avoid overthinking it too much. I don't usually spend more than a couple hours on this part.

Rough out the shape and go
I can't quite explain this part of the process well, as I don't really think about it. Start ripping out the negative space, be quick and rough about it, all the refinement can come later. (This is a great stress reliever.) If you need more depth, glue on more layers of foam and carve until satisfied.

As you add more parts, don't forget to size them against finished pieces. Abduct your friends and force them to model for you!

Refine refine refine
Once you've got the rough shape, sand it down. Then take a step back, measure, look at it in the mirror to catch stuff you've gotten too used to looking at, and hack away at it again. Sand again. (Never too much sanding.) Feel free to throw in some other materials in there. Remember, none of this will be in the finished product, only the shape. It can be as fragile as you like so long as it doesn't contain sulfur.

Spackle dat shit
Spackling is the stuff you use to patch the wall you make in your house you make after putting your head through it after working with spackle for an hour. It goes on easy, dries in an hour, sands just as easy, and gets EVERYWHERE. I have tracked this down the length of the entire maker shop I rent out space of, and it will never leave that place. It'll help you make a nice finished surface on your sculpt and buff out all those spongy foam areas and cracks where you hotglued spots together. I generaly spackle the entire surface and sand down.

No really, keep doing it. You're not going to get a second chance at this, what cures in rubber sillicone stays in rubber silicone- and in every piece you cast from it. Forever. Until you sand that. Sand now to avoid sanding later multiple times in a much less forgiving material.

You haven't sanded enough yet. Keep going.

Gear up
You'll want clothes you'll never wear again, gloves, and a respirator- which you should have been wearing for the sanding. While the silicone isn't bad, the plastic will certainly give you some serious headaches.

Mix up your rubber
Every rubber is going to be different, if you're using rebound I can give you some simple instruction, but there's much better guides you'll find on youtube with friendly, helpful people with cameras who'll do a better job of it. Generally, you'll be fishing it out of a gallon tub with wide popsicle sticks for a roughly 50/50 mix in a cup or some disposable container. I like smooth-on's little plastic measuring pots.

Slime it
You want your first layer to be thin. Paint it on with a brush or smooth it flat with a stick to press out as many airbubbles as possible. It'll go on thick and drip onto everything. Don't feel shy about slopping it back ontop when it slides off. Every bit thicker is a bit more inclined the mold will be to hold its shape.

Slime it moooore
Using a thickening agent like Thi-vex, thicken up the rubber to the consistency of peanut butter and spread it thick over the surface of your model. You'll want it to be able to hold its own shape to a certain degree. Try to get at least 3 or 4 layers, the outer layers without the thi-vex so you can get a nice smooth finish. You'll also want to add registration marks, these can be made out of just about anything, but are little nubs that stick out of your mold to help it align with the shell we're making next.

Make a shell
Most parts will require a support shell to help it keep its shape as you're casting a new part. I have had mixed results with smooth-on's plasti-paste, mostly due to the nature of how I work (fast, and with only a modicum of attention paid to precise measurements.) I've had better luck with the pieces I've nested into a box and expanding foam.

Don't forget, you need to be able to remove these molds from their new shell home, which means if they're particularly round, you'll most likely need to make a Two-Part Mold. Look this up on you-tube, as it's a tutorial and a skill in and of itself.

Take it all apart and get ready to mold
There's a good chance that if your piece is particularly round, you've gone and gotten it stuck inside the shell. I did this with two out of the three pauldrons and needed a friend to remove the third. This means you'll most likely have to rip the foam master mold apart to get it out, which can be a little heart wrenching but the finished mold should be fine. The rotocasted pieces tend to be more forgiving when it comes to flexibility.

There's a good chance your rubber silicone ripped out some spackling as well. Go ahead and remove these from the shells and wash out the spackling then settle the pink, silicone mold back down into the shell so that all the registration marks match up.

Mixing up your plastic
This is generally a bit easier than the silicone, but again, it will GET EVERYWHERE, so once that second part is in there it's game on and the resin takes no prisoners. For this reason, make sure to add the pigment to either the A or B part before mixing so you have lots of time to stir. The pot life for this stuff tends to be short, so you'll want to get it in there quickly.

Generally, you'll want to measure out just enough to coat every surface or else you're going to end up with extra deposits  and tell-tale slush marks. I was terrible about this and routinely added too much- and paid a cost for my insolence in sanding and wasted resin.

Slime it, part two
Toss your resin into the mold and start slushing it around so that it coats every surface, keep doing so and eventually you'll see the color start to change as it kicks. Once this has happened it's time to do it again. And again. And again. You'll find that each piece will require a different thickness to hold up to the rigors of existence, and it will be a magic number you will learn to approximate with experience. I generally tried not to go thinner than an 1/8th of an inch, but there were parts of our helmets that were nearly 1/3rd of an inch just in case they were dropped.

You will want to remove it to see your hard work. Don't. Resist. For now. Give it at least an hour or until it cools down ENTIRELY, or else it'll start to flatten and warp and won't you look stupid. (Like I did, nearly a half dozen times.) If you succumb to temptation, try to put it back in the mold when you're done being a curious asshole so you don't waste your time molding and $x worth of resin.

Tool off that flashing
There will be plastic bits and spill-over, it's just a fact of life. If you act now you can trim it off with a sharp exacto, but after it's entirely cool you'll be tooling it with a dremmel just to make any progress.

If you guessed sanding, you guessed right. Here's your chance to fix any bowed portions from missed registration marks, odd edges, air bubbles or other imperfections. Try to get your hands on a rotary sander, it's the best thing since sliced bread.

Annnd enjoy!
Here comes the sane part, painting and adding strapes/fabric/whatever the hell you're sticking it on. You know, the sane stuff that doesn't require respirators or chemical burns. Have fun, you've earned it.

Thanks for having a look, happy making!

« Last Edit: September 28, 2016, 09:52:55 AM by The Kaiser »

Offline Waxx

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Re: Cadian Standard Flack - An adventure in rotocasting
« Reply #1 on: September 09, 2014, 07:39:04 PM »
Great post. This answers a lot of questions I had about your build! Thanks a lot!

Offline Rraijjar

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Re: Cadian Standard Flack - An adventure in rotocasting
« Reply #2 on: September 11, 2014, 02:55:16 AM »
 :o that was a lot of info... just awesome ^^

Offline Capt.

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Re: Cadian Standard Flack - An adventure in rotocasting
« Reply #3 on: September 12, 2014, 01:19:26 AM »
Wow! That was brilliant- (and thorough) I'll never do it, but it was fascinating to read and inspiring to look at! Great post.

Offline The Kaiser

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Re: Cadian Standard Flack - An adventure in rotocasting
« Reply #4 on: September 15, 2014, 12:54:32 PM »
Glad you guys enjoyed it! Even if you don't ever use rotocasting, now you at least know about it. :)

Obscurus Crusade  |  Costuming  |  Imperial Guard & Imperium  |  Cadian Standard Flack - An adventure in rotocasting

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